Funny, as an elementary school teacher, the kids love the extra fun that comes at Christmas time.
When I worked in a Catholic school, we could have lots of fun, but the point was that baby Jesus was celebrating his birthday. Decorations fell along those lines. Nativity creches were common.
When I worked in public school, no nativity and no Jesus were allowed because of the separation or church and state in the US. We had lots of Santa and snowmen. We watched The Polar Express the last day of school before Winter break. We studied other celebrations like Hannukah and Kwanzaa. We were allowed to put up Christmas trees in the classroom. I usually bought giant snowflakes to hang from the ceiling. I made sure my kids had little bags of goodies like pencils, stickers, bouncing balls, candy, etc. And we had a little party with games. My kids lived in poverty and that might be all they got so I tried to make it festive before they left for the week or so of Winter Break.